Courageous gliders in the Argentinean Andes. Just like the surfers in Hawaii waiting for the perfect wave, the gliders look for waves made of wind behind the mountains, in an altitude of 12,000 m. With the help of these so-called lee-waves they succeed in setting new altitude records for gliders. However, these waves are also capricious and have often caused air crashes with passenger planes. A small group of scientists and pilots – amongst them the world record holder in gliding, Klaus Ohlmann – sets off with gliders to explore this dangerous phenomenon. The insights gained from their flights can make aviation safer.